Screen Printing - February/March 2018 - 28

Printing the Ultimate
Though white is traditional, using other colors for your underbases
can help you create incredible designs on dark garments.
Thomas Trimingham

he best artwork, and often the friendliest in production,
breaks the rules. One of the commonly understood rules of
getting the brightest hues possible on dark shirts is to start with
a white underbase. On a black shirt in particular, if the underbase doesn't properly block the color of the garment, there can
be an unexpected muting of the entire image or a shift to the
colors that are printed later. Prints that are dull or look different
than the original art the clients approved (typically a digital file
they viewed on their computer) can upset them and even make
them doubt the quality of your company. This issue can cost you
business, so it needs to be taken seriously.
This fear that orders will be rejected is one reason that the
majority of screen printers standardize the practice of printing
a solid-looking white underbase whenever they are working
with dark garments. The majority of the time, using a white
underbase isn't a bad idea. It is predictable, repeatable, and
will certainly give you the brightest, most saturated colors. It
can be extremely difficult to achieve certain colors like fire
engine reds and deep royal blues without a white underbase.
But there are some situations when using a different color
for the underbase will produce a much better print than using
white. (And one of them isn't when you run out of white
ink.) The choice begins with the design concept and the final
effect you want to achieve. It's much better to consider the
possibilities before you have printed several dozen shirts.

Underbase 101
Before we dive into when and how to use an underbase that
isn't white, it's a good idea to review what underbases do and
why white usually works so well. Knowing how an underbase
works will help you come up with ideas for alternate colors
and strategies.
Fundamentally, underbases do two things in creating a
foundation for the overprint colors:
1. They block the color of the garment as well as the
individual fibers of the material.
2. They create a reflective surface that will make the
subsequent colors appear brighter and more saturated.
Blocking out the shirt color and matting down its fibers is
an underbase's most important job. When using plastisol inks,
print the underbase with light squeegee pressure so that the
ink isn't pushed into the garment. The higher the underbase
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"sits" on the surface of the shirt, the brighter it will look and
the more shirt fibers it will cover, benefits that are lost when
squeegee pressure is excessive. Some printers try to counter
this problem by double printing (and double flashing) the
underbase in an attempt to better seal off the background. (I
call this approach "revolvering" because it forces you to index
the press in the wrong direction.) This just isn't a profitable
way to produce T-shirts, so avoid that technique whenever
possible. With the right screen and minimal squeegee pressure,
you shouldn't have to resort to double printing the underbase.
Regarding reflectivity, the simplest way to envision this is to
run a colorful photo through an inkjet printer on bright, white
paper, and then print it again using a gray or black stock. You will
quickly notice that the darker paper makes the top colors appear
much duller. (On a black paper, they may not even be visible.)
The reason images appear brighter on a white underbase is that
almost all inks are somewhat transparent. In the case of deep,
saturated colors like bright red, royal blue, and lemon yellow, the
pigments in these inks are like stained glass windows. They
create these bright colors by capturing every other color except
the one they let through. So a royal blue pigment traps every
color wavelength except bright blue, which is what our eyes see.
figure 1

Table of Contents for the Digital Edition of Screen Printing - February/March 2018